This project proposes studies of individuals suffering clinically overt, symptomatic AIDS dementia complex (ADC), as well as patients with AIDS who are at high risk for developing the ADC, in order to more precisely characterize the neurological and neuropsychological manifestations of this syndrome, as well as its immunological, virological and neuroradiological correlates, and its natural history. Clinical characterization will be accomplished by both cross-sectional and prospective/longitudinal studies to define the relative incidence, clinical presentation and evolution of the ADC. The neurological and neuropsychological data will then be correlate with systemic disease status, immunological function, virological findings in CSF and blood, and neuroradiological abnormalities including brain atrophy as define by computerized tomography (CT) and white matter changes revealed by magnetic resonance imaging (MRI). Patients will also be assessed with respect to their response to antiviral therapy. These studies will additionally contribute to refining neurological and neuropsychological instrumentation for evaluating the ADC. The data obtained in this Project will be combined with that derived from Projects 2 and 3, which examine individuals at earlier stages of HIV infection in order to derive a broad picture of the evolution and natural history of the ADC. In addition, this Project provides background clinical, neuropsychological and neuroradiological information pertinent to patients studied in Project 4 and to virological studies described in Project 5.